diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 29f203c6f10eeeed194670aa37956a6190e8e7a1..e8907709bd90a6342384dfb6f10b00e55018d65d 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -26,6 +26,8 @@
#include "nodes/makefuncs.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
+#include "optimizer/planmain.h"
+#include "optimizer/restrictinfo.h"
#include "utils/rel.h"
PG_MODULE_MAGIC;
@@ -48,7 +50,7 @@ struct FileFdwOption
* Note: If you are adding new option for user mapping, you need to modify
* fileGetOptions(), which currently doesn't bother to look at user mappings.
*/
-static struct FileFdwOption valid_options[] = {
+static const struct FileFdwOption valid_options[] = {
/* File options */
{"filename", ForeignTableRelationId},
@@ -71,6 +73,17 @@ static struct FileFdwOption valid_options[] = {
{NULL, InvalidOid}
};
+/*
+ * FDW-specific information for RelOptInfo.fdw_private.
+ */
+typedef struct FileFdwPlanState
+{
+ char *filename; /* file to read */
+ List *options; /* merged COPY options, excluding filename */
+ BlockNumber pages; /* estimate of file's physical size */
+ double ntuples; /* estimate of number of rows in file */
+} FileFdwPlanState;
+
/*
* FDW-specific information for ForeignScanState.fdw_state.
*/
@@ -93,9 +106,18 @@ PG_FUNCTION_INFO_V1(file_fdw_validator);
/*
* FDW callback routines
*/
-static void filePlanForeignScan(Oid foreigntableid,
- PlannerInfo *root,
- RelOptInfo *baserel);
+static void fileGetForeignRelSize(PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid);
+static void fileGetForeignPaths(PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid);
+static ForeignScan *fileGetForeignPlan(PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid,
+ ForeignPath *best_path,
+ List *tlist,
+ List *scan_clauses);
static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
static void fileBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
@@ -109,8 +131,10 @@ static bool is_valid_option(const char *option, Oid context);
static void fileGetOptions(Oid foreigntableid,
char **filename, List **other_options);
static List *get_file_fdw_attribute_options(Oid relid);
+static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
+ FileFdwPlanState *fdw_private);
static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
- const char *filename,
+ FileFdwPlanState *fdw_private,
Cost *startup_cost, Cost *total_cost);
@@ -123,7 +147,9 @@ file_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *fdwroutine = makeNode(FdwRoutine);
- fdwroutine->PlanForeignScan = filePlanForeignScan;
+ fdwroutine->GetForeignRelSize = fileGetForeignRelSize;
+ fdwroutine->GetForeignPaths = fileGetForeignPaths;
+ fdwroutine->GetForeignPlan = fileGetForeignPlan;
fdwroutine->ExplainForeignScan = fileExplainForeignScan;
fdwroutine->BeginForeignScan = fileBeginForeignScan;
fdwroutine->IterateForeignScan = fileIterateForeignScan;
@@ -177,7 +203,7 @@ file_fdw_validator(PG_FUNCTION_ARGS)
if (!is_valid_option(def->defname, catalog))
{
- struct FileFdwOption *opt;
+ const struct FileFdwOption *opt;
StringInfoData buf;
/*
@@ -249,7 +275,7 @@ file_fdw_validator(PG_FUNCTION_ARGS)
static bool
is_valid_option(const char *option, Oid context)
{
- struct FileFdwOption *opt;
+ const struct FileFdwOption *opt;
for (opt = valid_options; opt->optname; opt++)
{
@@ -381,7 +407,31 @@ get_file_fdw_attribute_options(Oid relid)
}
/*
- * filePlanForeignScan
+ * fileGetForeignRelSize
+ * Obtain relation size estimates for a foreign table
+ */
+static void
+fileGetForeignRelSize(PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid)
+{
+ FileFdwPlanState *fdw_private;
+
+ /*
+ * Fetch options. We only need filename at this point, but we might
+ * as well get everything and not need to re-fetch it later in planning.
+ */
+ fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
+ fileGetOptions(foreigntableid,
+ &fdw_private->filename, &fdw_private->options);
+ baserel->fdw_private = (void *) fdw_private;
+
+ /* Estimate relation size */
+ estimate_size(root, baserel, fdw_private);
+}
+
+/*
+ * fileGetForeignPaths
* Create possible access paths for a scan on the foreign table
*
* Currently we don't support any push-down feature, so there is only one
@@ -389,20 +439,16 @@ get_file_fdw_attribute_options(Oid relid)
* the data file.
*/
static void
-filePlanForeignScan(Oid foreigntableid,
- PlannerInfo *root,
- RelOptInfo *baserel)
+fileGetForeignPaths(PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid)
{
- char *filename;
- List *options;
+ FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
Cost startup_cost;
Cost total_cost;
- /* Fetch options --- we only need filename at this point */
- fileGetOptions(foreigntableid, &filename, &options);
-
- /* Estimate costs and update baserel->rows */
- estimate_costs(root, baserel, filename,
+ /* Estimate costs */
+ estimate_costs(root, baserel, fdw_private,
&startup_cost, &total_cost);
/* Create a ForeignPath node and add it as only possible path */
@@ -422,6 +468,37 @@ filePlanForeignScan(Oid foreigntableid,
*/
}
+/*
+ * fileGetForeignPlan
+ * Create a ForeignScan plan node for scanning the foreign table
+ */
+static ForeignScan *
+fileGetForeignPlan(PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid,
+ ForeignPath *best_path,
+ List *tlist,
+ List *scan_clauses)
+{
+ Index scan_relid = baserel->relid;
+
+ /*
+ * We have no native ability to evaluate restriction clauses, so we just
+ * put all the scan_clauses into the plan node's qual list for the
+ * executor to check. So all we have to do here is strip RestrictInfo
+ * nodes from the clauses and ignore pseudoconstants (which will be
+ * handled elsewhere).
+ */
+ scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+ /* Create the ForeignScan node */
+ return make_foreignscan(tlist,
+ scan_clauses,
+ scan_relid,
+ NIL, /* no expressions to evaluate */
+ NIL); /* no private state either */
+}
+
/*
* fileExplainForeignScan
* Produce extra output for EXPLAIN
@@ -568,38 +645,38 @@ fileReScanForeignScan(ForeignScanState *node)
}
/*
- * Estimate costs of scanning a foreign table.
+ * Estimate size of a foreign table.
*
- * In addition to setting *startup_cost and *total_cost, this should
- * update baserel->rows.
+ * The main result is returned in baserel->rows. We also set
+ * fdw_private->pages and fdw_private->ntuples for later use in the cost
+ * calculation.
*/
static void
-estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
- const char *filename,
- Cost *startup_cost, Cost *total_cost)
+estimate_size(PlannerInfo *root, RelOptInfo *baserel,
+ FileFdwPlanState *fdw_private)
{
struct stat stat_buf;
BlockNumber pages;
int tuple_width;
double ntuples;
double nrows;
- Cost run_cost = 0;
- Cost cpu_per_tuple;
/*
* Get size of the file. It might not be there at plan time, though, in
* which case we have to use a default estimate.
*/
- if (stat(filename, &stat_buf) < 0)
+ if (stat(fdw_private->filename, &stat_buf) < 0)
stat_buf.st_size = 10 * BLCKSZ;
/*
- * Convert size to pages for use in I/O cost estimate below.
+ * Convert size to pages for use in I/O cost estimate later.
*/
pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
if (pages < 1)
pages = 1;
+ fdw_private->pages = pages;
+
/*
* Estimate the number of tuples in the file. We back into this estimate
* using the planner's idea of the relation width; which is bogus if not
@@ -611,6 +688,8 @@ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
ntuples = clamp_row_est((double) stat_buf.st_size / (double) tuple_width);
+ fdw_private->ntuples = ntuples;
+
/*
* Now estimate the number of rows returned by the scan after applying the
* baserestrictinfo quals. This is pretty bogus too, since the planner
@@ -627,12 +706,28 @@ estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
/* Save the output-rows estimate for the planner */
baserel->rows = nrows;
+}
+
+/*
+ * Estimate costs of scanning a foreign table.
+ *
+ * Results are returned in *startup_cost and *total_cost.
+ */
+static void
+estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+ FileFdwPlanState *fdw_private,
+ Cost *startup_cost, Cost *total_cost)
+{
+ BlockNumber pages = fdw_private->pages;
+ double ntuples = fdw_private->ntuples;
+ Cost run_cost = 0;
+ Cost cpu_per_tuple;
/*
- * Now estimate costs. We estimate costs almost the same way as
- * cost_seqscan(), thus assuming that I/O costs are equivalent to a
- * regular table file of the same size. However, we take per-tuple CPU
- * costs as 10x of a seqscan, to account for the cost of parsing records.
+ * We estimate costs almost the same way as cost_seqscan(), thus assuming
+ * that I/O costs are equivalent to a regular table file of the same size.
+ * However, we take per-tuple CPU costs as 10x of a seqscan, to account
+ * for the cost of parsing records.
*/
run_cost += seq_page_cost * pages;
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index dbfcbbc2b36dd49b0f0a8ffc9893da0b2a25a891..f7bf3d8a39571380ca6c28a972216684fa6a31bb 100644
--- a/doc/src/sgml/fdwhandler.sgml
+++ b/doc/src/sgml/fdwhandler.sgml
@@ -89,52 +89,92 @@
<para>
<programlisting>
void
-PlanForeignScan (Oid foreigntableid,
- PlannerInfo *root,
- RelOptInfo *baserel);
+GetForeignRelSize (PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid);
</programlisting>
- Create possible access paths for a scan on a foreign table. This is
- called when a query is planned.
+ Obtain relation size estimates for a foreign table. This is called
+ at the beginning of planning for a query involving a foreign table.
+ <literal>root</> is the planner's global information about the query;
+ <literal>baserel</> is the planner's information about this table; and
<literal>foreigntableid</> is the <structname>pg_class</> OID of the
- foreign table. <literal>root</> is the planner's global information
- about the query, and <literal>baserel</> is the planner's information
- about this table.
+ foreign table. (<literal>foreigntableid</> could be obtained from the
+ planner data structures, but it's passed explicitly to save effort.)
</para>
<para>
- The function must generate at least one access path (ForeignPath node)
- for a scan on the foreign table and must call <function>add_path</> to
- add the path to <literal>baserel->pathlist</>. It's recommended to
- use <function>create_foreignscan_path</> to build the ForeignPath node.
- The function may generate multiple access paths, e.g., a path which has
- valid <literal>pathkeys</> to represent a pre-sorted result. Each access
- path must contain cost estimates, and can contain any FDW-private
- information that is needed to execute the foreign scan at a later time.
- (Note that the private information must be represented in a form that
- <function>copyObject</> knows how to copy.)
+ This function should update <literal>baserel->rows</> to be the
+ expected number of rows returned by the table scan, after accounting for
+ the filtering done by the restriction quals. The initial value of
+ <literal>baserel->rows</> is just a constant default estimate, which
+ should be replaced if at all possible. The function may also choose to
+ update <literal>baserel->width</> if it can compute a better estimate
+ of the average result row width.
</para>
<para>
- The information in <literal>root</> and <literal>baserel</> can be used
- to reduce the amount of information that has to be fetched from the
- foreign table (and therefore reduce the cost estimate).
- <literal>baserel->baserestrictinfo</> is particularly interesting, as
- it contains restriction quals (<literal>WHERE</> clauses) that can be
- used to filter the rows to be fetched. (The FDW is not required to
- enforce these quals, as the finished plan will recheck them anyway.)
- <literal>baserel->reltargetlist</> can be used to determine which
- columns need to be fetched.
+ See <xref linkend="fdw-planning"> for additional information.
+ </para>
+
+ <para>
+<programlisting>
+void
+GetForeignPaths (PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid);
+</programlisting>
+
+ Create possible access paths for a scan on a foreign table.
+ This is called during query planning.
+ The parameters are the same as for <function>GetForeignRelSize</>,
+ which has already been called.
+ </para>
+
+ <para>
+ This function must generate at least one access path
+ (<structname>ForeignPath</> node) for a scan on the foreign table and
+ must call <function>add_path</> to add each such path to
+ <literal>baserel->pathlist</>. It's recommended to use
+ <function>create_foreignscan_path</> to build the
+ <structname>ForeignPath</> nodes. The function can generate multiple
+ access paths, e.g., a path which has valid <literal>pathkeys</> to
+ represent a pre-sorted result. Each access path must contain cost
+ estimates, and can contain any FDW-private information that is needed to
+ identify the specific scan method intended.
+ </para>
+
+ <para>
+ See <xref linkend="fdw-planning"> for additional information.
+ </para>
+
+ <para>
+<programlisting>
+ForeignScan *
+GetForeignPlan (PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid,
+ ForeignPath *best_path,
+ List *tlist,
+ List *scan_clauses);
+</programlisting>
+
+ Create a <structname>ForeignScan</> plan node from the selected foreign
+ access path. This is called at the end of query planning.
+ The parameters are as for <function>GetForeignRelSize</>, plus
+ the selected <structname>ForeignPath</> (previously produced by
+ <function>GetForeignPaths</>), the target list to be emitted by the
+ plan node, and the restriction clauses to be enforced by the plan node.
</para>
<para>
- In addition to returning cost estimates, the function should update
- <literal>baserel->rows</> to be the expected number of rows returned
- by the scan, after accounting for the filtering done by the restriction
- quals. The initial value of <literal>baserel->rows</> is just a
- constant default estimate, which should be replaced if at all possible.
- The function may also choose to update <literal>baserel->width</> if
- it can compute a better estimate of the average result row width.
+ This function must create and return a <structname>ForeignScan</> plan
+ node; it's recommended to use <function>make_foreignscan</> to build the
+ <structname>ForeignScan</> node.
+ </para>
+
+ <para>
+ See <xref linkend="fdw-planning"> for additional information.
</para>
<para>
@@ -170,7 +210,7 @@ BeginForeignScan (ForeignScanState *node,
the table to scan is accessible through the
<structname>ForeignScanState</> node (in particular, from the underlying
<structname>ForeignScan</> plan node, which contains any FDW-private
- information provided by <function>PlanForeignScan</>).
+ information provided by <function>GetForeignPlan</>).
</para>
<para>
@@ -347,6 +387,126 @@ GetForeignServerByName(const char *name, bool missing_ok);
return NULL if missing_ok is true, otherwise raise an error.
</para>
+ </sect1>
+
+ <sect1 id="fdw-planning">
+ <title>Foreign Data Wrapper Query Planning</title>
+
+ <para>
+ The FDW callback functions <function>GetForeignRelSize</>,
+ <function>GetForeignPaths</>, and <function>GetForeignPlan</> must fit
+ into the workings of the <productname>PostgreSQL</> planner. Here are
+ some notes about what they must do.
+ </para>
+
+ <para>
+ The information in <literal>root</> and <literal>baserel</> can be used
+ to reduce the amount of information that has to be fetched from the
+ foreign table (and therefore reduce the cost).
+ <literal>baserel->baserestrictinfo</> is particularly interesting, as
+ it contains restriction quals (<literal>WHERE</> clauses) that should be
+ used to filter the rows to be fetched. (The FDW itself is not required
+ to enforce these quals, as the core executor can check them instead.)
+ <literal>baserel->reltargetlist</> can be used to determine which
+ columns need to be fetched; but note that it only lists columns that
+ have to be emitted by the <structname>ForeignScan</> plan node, not
+ columns that are used in qual evaluation but not output by the query.
+ </para>
+
+ <para>
+ Various private fields are available for the FDW planning functions to
+ keep information in. Generally, whatever you store in FDW private fields
+ should be palloc'd, so that it will be reclaimed at the end of planning.
+ </para>
+
+ <para>
+ <literal>baserel->fdw_private</> is a <type>void</> pointer that is
+ available for FDW planning functions to store information relevant to
+ the particular foreign table. The core planner does not touch it except
+ to initialize it to NULL when the <literal>baserel</> node is created.
+ It is useful for passing information forward from
+ <function>GetForeignRelSize</> to <function>GetForeignPaths</> and/or
+ <function>GetForeignPaths</> to <function>GetForeignPlan</>, thereby
+ avoiding recalculation.
+ </para>
+
+ <para>
+ <function>GetForeignPaths</> can identify the meaning of different
+ access paths by storing private information in the
+ <structfield>fdw_private</> field of <structname>ForeignPath</> nodes.
+ <structfield>fdw_private</> is declared as a <type>List</> pointer, but
+ could actually contain anything since the core planner does not touch
+ it. However, best practice is to use a representation that's dumpable
+ by <function>nodeToString</>, for use with debugging support available
+ in the backend.
+ </para>
+
+ <para>
+ <function>GetForeignPlan</> can examine the <structfield>fdw_private</>
+ field of the selected <structname>ForeignPath</> node, and can generate
+ <structfield>fdw_exprs</> and <structfield>fdw_private</> lists to be
+ placed in the <structname>ForeignScan</> plan node, where they will be
+ available at execution time. Both of these lists must be
+ represented in a form that <function>copyObject</> knows how to copy.
+ The <structfield>fdw_private</> list has no other restrictions and is
+ not interpreted by the core backend in any way. The
+ <structfield>fdw_exprs</> list, if not NIL, is expected to contain
+ expression trees that are intended to be executed at runtime. These
+ trees will undergo post-processing by the planner to make them fully
+ executable.
+ </para>
+
+ <para>
+ In <function>GetForeignPlan</>, generally the passed-in targetlist can
+ be copied into the plan node as-is. The passed scan_clauses list
+ contains the same clauses as <literal>baserel->baserestrictinfo</>,
+ but may be re-ordered for better execution efficiency. In simple cases
+ the FDW can just strip <structname>RestrictInfo</> nodes from the
+ scan_clauses list (using <function>extract_actual_clauses</>) and put
+ all the clauses into the plan node's qual list, which means that all the
+ clauses will be checked by the executor at runtime. More complex FDWs
+ may be able to check some of the clauses internally, in which case those
+ clauses can be removed from the plan node's qual list so that the
+ executor doesn't waste time rechecking them.
+ </para>
+
+ <para>
+ As an example, the FDW might identify some restriction clauses of the
+ form <replaceable>foreign_variable</> <literal>=</>
+ <replaceable>sub_expression</>, which it determines can be executed on
+ the remote server given the locally-evaluated value of the
+ <replaceable>sub_expression</>. The actual identification of such a
+ clause should happen during <function>GetForeignPaths</>, since it would
+ affect the cost estimate for the path. The path's
+ <structfield>fdw_private</> field would probably include a pointer to
+ the identified clause's <structname>RestrictInfo</> node. Then
+ <function>GetForeignPlan</> would remove that clause from scan_clauses,
+ but add the <replaceable>sub_expression</> to <structfield>fdw_exprs</>
+ to ensure that it gets massaged into executable form. It would probably
+ also put control information into the plan node's
+ <structfield>fdw_private</> field to tell the execution functions what
+ to do at runtime. The query transmitted to the remote server would
+ involve something like <literal>WHERE <replaceable>foreign_variable</> =
+ $1</literal>, with the parameter value obtained at runtime from
+ evaluation of the <structfield>fdw_exprs</> expression tree.
+ </para>
+
+ <para>
+ The FDW should always construct at least one path that depends only on
+ the table's restriction clauses. In join queries, it might also choose
+ to construct path(s) that depend on join clauses, for example
+ <replaceable>foreign_variable</> <literal>=</>
+ <replaceable>local_variable</>. Such clauses will not be found in
+ <literal>baserel->baserestrictinfo</> but must be sought in the
+ relation's join lists. A path using such a clause is called a
+ <quote>parameterized path</>. It must show the other relation(s) as
+ <literal>required_outer</> and list the specific join clause(s) in
+ <literal>param_clauses</>. In <function>GetForeignPlan</>, the
+ <replaceable>local_variable</> portion of the join clause would be added
+ to <structfield>fdw_exprs</>, and then at runtime the case works the
+ same as for an ordinary restriction clause.
+ </para>
+
</sect1>
</chapter>
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 868fb7130a8b28cf3e074d7d3903e58366c0c914..5cde22543f5b7d4d607224acfa22a604a419ed63 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -591,8 +591,9 @@ _copyForeignScan(const ForeignScan *from)
/*
* copy remainder of node
*/
- COPY_SCALAR_FIELD(fsSystemCol);
+ COPY_NODE_FIELD(fdw_exprs);
COPY_NODE_FIELD(fdw_private);
+ COPY_SCALAR_FIELD(fsSystemCol);
return newnode;
}
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 9daeb3e7b43e911aeab25b7521d41191928499bd..51181a9a7438e8609ab922340d1c2d20ba73726d 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -559,8 +559,9 @@ _outForeignScan(StringInfo str, const ForeignScan *node)
_outScanInfo(str, (const Scan *) node);
- WRITE_BOOL_FIELD(fsSystemCol);
+ WRITE_NODE_FIELD(fdw_exprs);
WRITE_NODE_FIELD(fdw_private);
+ WRITE_BOOL_FIELD(fsSystemCol);
}
static void
@@ -1741,6 +1742,7 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
WRITE_FLOAT_FIELD(allvisfrac, "%.6f");
WRITE_NODE_FIELD(subplan);
WRITE_NODE_FIELD(subroot);
+ /* we don't try to print fdwroutine or fdw_private */
WRITE_NODE_FIELD(baserestrictinfo);
WRITE_NODE_FIELD(joininfo);
WRITE_BOOL_FIELD(has_eclass_joins);
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 6e81ce0fc26496f73e89d5048b0fd8a19da33b74..03c604a03d6f37d9d6d975fd0809429c56d61b38 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -396,6 +396,12 @@ set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
/* Mark rel with estimated output rows, width, etc */
set_foreign_size_estimates(root, rel);
+
+ /* Get FDW routine pointers for the rel */
+ rel->fdwroutine = GetFdwRoutineByRelId(rte->relid);
+
+ /* Let FDW adjust the size estimates, if it can */
+ rel->fdwroutine->GetForeignRelSize(root, rel, rte->relid);
}
/*
@@ -405,11 +411,8 @@ set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
static void
set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
- FdwRoutine *fdwroutine;
-
- /* Call the FDW's PlanForeignScan function to generate path(s) */
- fdwroutine = GetFdwRoutineByRelId(rte->relid);
- fdwroutine->PlanForeignScan(rte->relid, root, rel);
+ /* Call the FDW's GetForeignPaths function to generate path(s) */
+ rel->fdwroutine->GetForeignPaths(root, rel, rte->relid);
/* Select cheapest path */
set_cheapest(rel);
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 885d8558c319fd283df351c2c8e062a449b72d3c..24c853d47ef1aabb95156f90be4a8f3ea3d4995e 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -3745,7 +3745,7 @@ set_cte_size_estimates(PlannerInfo *root, RelOptInfo *rel, Plan *cteplan)
* using what will be purely datatype-driven estimates from the targetlist.
* There is no way to do anything sane with the rows value, so we just put
* a default estimate and hope that the wrapper can improve on it. The
- * wrapper's PlanForeignScan function will be called momentarily.
+ * wrapper's GetForeignRelSize function will be called momentarily.
*
* The rel's targetlist and restrictinfo list must have been constructed
* already.
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index b1df56cafd25abfda40657555a1c832aa6db797a..94140d304f754236955452e26b80de8276ca729b 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -20,6 +20,7 @@
#include <math.h>
#include "access/skey.h"
+#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
@@ -119,8 +120,6 @@ static CteScan *make_ctescan(List *qptlist, List *qpqual,
Index scanrelid, int ctePlanId, int cteParam);
static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
Index scanrelid, int wtParam);
-static ForeignScan *make_foreignscan(List *qptlist, List *qpqual,
- Index scanrelid, bool fsSystemCol, List *fdw_private);
static BitmapAnd *make_bitmap_and(List *bitmapplans);
static BitmapOr *make_bitmap_or(List *bitmapplans);
static NestLoop *make_nestloop(List *tlist,
@@ -1816,7 +1815,6 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
RelOptInfo *rel = best_path->path.parent;
Index scan_relid = rel->relid;
RangeTblEntry *rte;
- bool fsSystemCol;
int i;
/* it should be a base rel... */
@@ -1825,31 +1823,56 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
rte = planner_rt_fetch(scan_relid, root);
Assert(rte->rtekind == RTE_RELATION);
- /* Sort clauses into best execution order */
+ /*
+ * Sort clauses into best execution order. We do this first since the
+ * FDW might have more info than we do and wish to adjust the ordering.
+ */
scan_clauses = order_qual_clauses(root, scan_clauses);
- /* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
- scan_clauses = extract_actual_clauses(scan_clauses, false);
+ /*
+ * Let the FDW perform its processing on the restriction clauses and
+ * generate the plan node. Note that the FDW might remove restriction
+ * clauses that it intends to execute remotely, or even add more (if it
+ * has selected some join clauses for remote use but also wants them
+ * rechecked locally).
+ */
+ scan_plan = rel->fdwroutine->GetForeignPlan(root, rel, rte->relid,
+ best_path,
+ tlist, scan_clauses);
+
+ /* Copy cost data from Path to Plan; no need to make FDW do this */
+ copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
- /* Detect whether any system columns are requested from rel */
- fsSystemCol = false;
+ /*
+ * Replace any outer-relation variables with nestloop params in the qual
+ * and fdw_exprs expressions. We do this last so that the FDW doesn't
+ * have to be involved. (Note that parts of fdw_exprs could have come
+ * from join clauses, so doing this beforehand on the scan_clauses
+ * wouldn't work.)
+ */
+ if (best_path->path.required_outer)
+ {
+ scan_plan->scan.plan.qual = (List *)
+ replace_nestloop_params(root, (Node *) scan_plan->scan.plan.qual);
+ scan_plan->fdw_exprs = (List *)
+ replace_nestloop_params(root, (Node *) scan_plan->fdw_exprs);
+ }
+
+ /*
+ * Detect whether any system columns are requested from rel. This is a
+ * bit of a kluge and might go away someday, so we intentionally leave it
+ * out of the API presented to FDWs.
+ */
+ scan_plan->fsSystemCol = false;
for (i = rel->min_attr; i < 0; i++)
{
if (!bms_is_empty(rel->attr_needed[i - rel->min_attr]))
{
- fsSystemCol = true;
+ scan_plan->fsSystemCol = true;
break;
}
}
- scan_plan = make_foreignscan(tlist,
- scan_clauses,
- scan_relid,
- fsSystemCol,
- best_path->fdw_private);
-
- copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
-
return scan_plan;
}
@@ -3183,24 +3206,26 @@ make_worktablescan(List *qptlist,
return node;
}
-static ForeignScan *
+ForeignScan *
make_foreignscan(List *qptlist,
List *qpqual,
Index scanrelid,
- bool fsSystemCol,
+ List *fdw_exprs,
List *fdw_private)
{
ForeignScan *node = makeNode(ForeignScan);
Plan *plan = &node->scan.plan;
- /* cost should be inserted by caller */
+ /* cost will be filled in by create_foreignscan_plan */
plan->targetlist = qptlist;
plan->qual = qpqual;
plan->lefttree = NULL;
plan->righttree = NULL;
node->scan.scanrelid = scanrelid;
- node->fsSystemCol = fsSystemCol;
+ node->fdw_exprs = fdw_exprs;
node->fdw_private = fdw_private;
+ /* fsSystemCol will be filled in by create_foreignscan_plan */
+ node->fsSystemCol = false;
return node;
}
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index e1b48fb4f53061f5b06653c67275dc0b323bffd0..69396694aaa9df0edbc361ede98b3f77db6724dc 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -428,6 +428,8 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
splan->scan.plan.qual =
fix_scan_list(root, splan->scan.plan.qual, rtoffset);
+ splan->fdw_exprs =
+ fix_scan_list(root, splan->fdw_exprs, rtoffset);
}
break;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 40a420a3546f12de37459881ed587d89ae6954c3..b64db1e1c0659ea9b6af25327f689b083de845e6 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2137,6 +2137,8 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
break;
case T_ForeignScan:
+ finalize_primnode((Node *) ((ForeignScan *) plan)->fdw_exprs,
+ &context);
context.paramids = bms_add_members(context.paramids, scan_params);
break;
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 6d1545476df7b054d48cae8a85669935d406c879..a2fc75a659e50ca7d5726ed9d024622af9e7f191 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1767,7 +1767,7 @@ create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel)
* returning the pathnode.
*
* This function is never called from core Postgres; rather, it's expected
- * to be called by the PlanForeignScan function of a foreign data wrapper.
+ * to be called by the GetForeignPaths function of a foreign data wrapper.
* We make the FDW supply all fields of the path, since we do not have any
* way to calculate them in core.
*/
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 0cdf638c1ddb1c614eb8ef3cd2ddea4571248ff6..cee092a8810102fdf48023e180739cd8dbc3d81c 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -113,6 +113,8 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
rel->allvisfrac = 0;
rel->subplan = NULL;
rel->subroot = NULL;
+ rel->fdwroutine = NULL;
+ rel->fdw_private = NULL;
rel->baserestrictinfo = NIL;
rel->baserestrictcost.startup = 0;
rel->baserestrictcost.per_tuple = 0;
@@ -366,6 +368,8 @@ build_join_rel(PlannerInfo *root,
joinrel->allvisfrac = 0;
joinrel->subplan = NULL;
joinrel->subroot = NULL;
+ joinrel->fdwroutine = NULL;
+ joinrel->fdw_private = NULL;
joinrel->baserestrictinfo = NIL;
joinrel->baserestrictcost.startup = 0;
joinrel->baserestrictcost.per_tuple = 0;
diff --git a/src/include/foreign/fdwapi.h b/src/include/foreign/fdwapi.h
index 9e135c62069fdc200e4f3cf58fa9725847d279fb..854f17755c4543ec85a66c6a6a3376fbcffd1cda 100644
--- a/src/include/foreign/fdwapi.h
+++ b/src/include/foreign/fdwapi.h
@@ -23,9 +23,20 @@ struct ExplainState;
* Callback function signatures --- see fdwhandler.sgml for more info.
*/
-typedef void (*PlanForeignScan_function) (Oid foreigntableid,
- PlannerInfo *root,
- RelOptInfo *baserel);
+typedef void (*GetForeignRelSize_function) (PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid);
+
+typedef void (*GetForeignPaths_function) (PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid);
+
+typedef ForeignScan *(*GetForeignPlan_function) (PlannerInfo *root,
+ RelOptInfo *baserel,
+ Oid foreigntableid,
+ ForeignPath *best_path,
+ List *tlist,
+ List *scan_clauses);
typedef void (*ExplainForeignScan_function) (ForeignScanState *node,
struct ExplainState *es);
@@ -53,7 +64,9 @@ typedef struct FdwRoutine
{
NodeTag type;
- PlanForeignScan_function PlanForeignScan;
+ GetForeignRelSize_function GetForeignRelSize;
+ GetForeignPaths_function GetForeignPaths;
+ GetForeignPlan_function GetForeignPlan;
ExplainForeignScan_function ExplainForeignScan;
BeginForeignScan_function BeginForeignScan;
IterateForeignScan_function IterateForeignScan;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 3962792d3d89a6d5077d1d682e2c3d112a6c568f..e6bb3239f4214c26aa1d70d4ca4ac50f63148ad5 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -462,13 +462,22 @@ typedef struct WorkTableScan
/* ----------------
* ForeignScan node
+ *
+ * fdw_exprs and fdw_private are both under the control of the foreign-data
+ * wrapper, but fdw_exprs is presumed to contain expression trees and will
+ * be post-processed accordingly by the planner; fdw_private won't be.
+ * Note that everything in both lists must be copiable by copyObject().
+ * One way to store an arbitrary blob of bytes is to represent it as a bytea
+ * Const. Usually, though, you'll be better off choosing a representation
+ * that can be dumped usefully by nodeToString().
* ----------------
*/
typedef struct ForeignScan
{
Scan scan;
- bool fsSystemCol; /* true if any "system column" is needed */
+ List *fdw_exprs; /* expressions that FDW may evaluate */
List *fdw_private; /* private data for FDW */
+ bool fsSystemCol; /* true if any "system column" is needed */
} ForeignScan;
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 2a686080059f3ffd26313798324323c6f2f6b56d..8616223f24a8cbe5424b89599b331538db05dd76 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -334,10 +334,13 @@ typedef struct PlannerInfo
* allvisfrac - fraction of disk pages that are marked all-visible
* subplan - plan for subquery (NULL if it's not a subquery)
* subroot - PlannerInfo for subquery (NULL if it's not a subquery)
+ * fdwroutine - function hooks for FDW, if foreign table (else NULL)
+ * fdw_private - private state for FDW, if foreign table (else NULL)
*
* Note: for a subquery, tuples, subplan, subroot are not set immediately
* upon creation of the RelOptInfo object; they are filled in when
- * set_base_rel_pathlist processes the object.
+ * set_subquery_pathlist processes the object. Likewise, fdwroutine
+ * and fdw_private are filled during initial path creation.
*
* For otherrels that are appendrel members, these fields are filled
* in just as for a baserel.
@@ -414,8 +417,12 @@ typedef struct RelOptInfo
BlockNumber pages; /* size estimates derived from pg_class */
double tuples;
double allvisfrac;
+ /* use "struct Plan" to avoid including plannodes.h here */
struct Plan *subplan; /* if subquery */
PlannerInfo *subroot; /* if subquery */
+ /* use "struct FdwRoutine" to avoid including fdwapi.h here */
+ struct FdwRoutine *fdwroutine; /* if foreign table */
+ void *fdw_private; /* if foreign table */
/* used by various scans and joins: */
List *baserestrictinfo; /* RestrictInfo structures (if base
@@ -793,14 +800,13 @@ typedef struct TidPath
} TidPath;
/*
- * ForeignPath represents a scan of a foreign table
- *
- * fdw_private contains FDW private data about the scan, which will be copied
- * to the final ForeignScan plan node so that it is available at execution
- * time. Note that everything in this list must be copiable by copyObject().
- * One way to store an arbitrary blob of bytes is to represent it as a bytea
- * Const. Usually, though, you'll be better off choosing a representation
- * that can be dumped usefully by nodeToString().
+ * ForeignPath represents a potential scan of a foreign table
+ *
+ * fdw_private stores FDW private data about the scan. While fdw_private is
+ * not actually touched by the core code during normal operations, it's
+ * generally a good idea to use a representation that can be dumped by
+ * nodeToString(), so that you can examine the structure during debugging
+ * with tools like pprint().
*/
typedef struct ForeignPath
{
diff --git a/src/include/optimizer/planmain.h b/src/include/optimizer/planmain.h
index 8bd603124b3ac8ab87af160646301c7bbf8dbf16..47cc39cf1d9c3646fb10b76e6c4a97e166e65e08 100644
--- a/src/include/optimizer/planmain.h
+++ b/src/include/optimizer/planmain.h
@@ -42,6 +42,8 @@ extern Plan *optimize_minmax_aggregates(PlannerInfo *root, List *tlist,
extern Plan *create_plan(PlannerInfo *root, Path *best_path);
extern SubqueryScan *make_subqueryscan(List *qptlist, List *qpqual,
Index scanrelid, Plan *subplan);
+extern ForeignScan *make_foreignscan(List *qptlist, List *qpqual,
+ Index scanrelid, List *fdw_exprs, List *fdw_private);
extern Append *make_append(List *appendplans, List *tlist);
extern RecursiveUnion *make_recursive_union(List *tlist,
Plan *lefttree, Plan *righttree, int wtParam,